Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $41.95   11.190%   $46.6442   $46.64   $46.65   $46.60  
  Purchase #2 $215.32   7.863%   $232.2506   $232.25   $232.25   $232.30  
  Purchase #3 $80.89   4.423%   $84.4678   $84.47   $84.45   $84.50  
  Purchase #4 $188.85   7.268%   $202.5756   $202.58   $202.60   $202.60  
  Purchase #5 $216.29   12.652%   $243.655   $243.66   $243.65   $243.70  
  Purchase #6 $139.60   5.482%   $147.2529   $147.25   $147.25   $147.30  
  Purchase #7 $165.46   13.504%   $187.8037   $187.80   $187.80   $187.80  
  7 purchase totals = $1,048.36       $1,144.6498   $1,144.65   $1,144.65   $1,144.80